California:

The first European to explore the coast as far north as the Russian River was the Portuguese João Rodrigues Cabrilho, in 1542, sailing for the Spanish Empire. Some 37 years later, the English explorer Francis Drake also explored and claimed an undefined portion of the California coast in 1579. Spanish traders made unintended visits with the Manila Galleons on their return trips from the Philippines beginning in 1565. Sebastián Vizcaíno explored and mapped the coast of California in 1602 for New Spain.

Spanish missionaries began setting up twenty-one California Missions along the coast of what became known as Alta California (Upper California), together with small towns and presidios. The first mission in Alta California was established at San Diego in 1769.  In 1821, the Mexican War of Independence gave Mexico (including California), independence from Spain; for the next twenty-five years, Alta California remained a remote northern province of the nation of Mexico. Cattle ranches, or ranchos, emerged as the dominant institutions of Mexican California. After Mexican independence from Spain, the chain of missions became the property of the Mexican government and were secularized by 1832. The ranchos developed under ownership by Californios (Spanish-speaking Californians) who had received land grants and traded cowhides and tallow with Boston merchants.

Beginning in the 1820s, trappers and settlers from the United States and Canada began to arrive in Northern California, harbingers of the great changes that would later sweep the Mexican territory. These new arrivals used the Siskiyou Trail, California Trail, Oregon Trail, and Old Spanish Trail to cross the rugged mountains and harsh deserts surrounding California. In this period, Imperial Russia explored the California coast and established a trading post at Fort Ross.

In 1846, settlers rebelled against Mexican rule during the Bear Flag Revolt. Afterwards, rebels raised the Bear Flag (featuring a bear, a star, a red stripe, and the words "California Republic") at Sonoma.

In 1848, the non-native population of California has been estimated to be no more than 15,000. But after gold was discovered, the population burgeoned with U.S. citizens, Europeans, and other immigrants during the great California Gold Rush. On September 9, 1850, as part of the Compromise of 1850, California was admitted to the United States as a free state (one in which slavery was prohibited).

The seat of government for California under Mexican rule was located at Monterey from 1777 until 1835, when Mexican authorities abandoned California, leaving their missions and military forts behind.  In 1849, the Constitutional Convention was first held there. Among the duties was the task of determining the location for the new State capital. The first legislative sessions were held in San Jose (1850-1851). Subsequent locations included Vallejo (1852-1853), and nearby Benicia (1853-1854), although these locations eventually proved to be inadequate as well. The capital has been located in Sacramento since 1854.

Travel between California and the central and eastern parts of the United States was time-consuming and dangerous. A more direct connection came in 1869 with the completion of the First Transcontinental Railroad through Donner Pass in the Sierra Nevada mountains. After this rail link was established, hundreds of thousands of U.S. citizens came west, where new Californians were discovering that land in the state, if irrigated during the dry summer months, was extremely well-suited to fruit cultivation and agriculture in general. Vast expanses of wheat and other cereal crops, vegetable crops, cotton, and nut and fruit trees were grown (including oranges in Southern California), and the foundation was laid for the state's prodigious agricultural production in the Central Valley and elsewhere.

During the early 20th century, migration to California accelerated with the completion of major transcontinental highways like the Lincoln Highway and Route 66. In the period from 1900 to 1965, the population grew from fewer than one million to become the most populous state in the Union. From 1965 to the present, the population changed radically and became one of the most diverse in the world. The state is regarded as a world center of technology and engineering businesses, of the entertainment and music industries, and as the U.S. center of agricultural production.